Spunlaced nonwovens as hook and loop fastener component

ABSTRACT

The present invention relates to the use of a spunlaced nonwoven fabric made of continuous filaments as loop material for hook and loop fasteners. The invention also relates to a loop material made of a nonwoven fabric and the production thereof.

The present invention relates to the use of spunlaced non-woven materials of continuous filaments as loop component of hook-and-loop fasteners as well as loop components for hook-and-loop fasteners of spunlaced non-woven materials of continuous filaments.

For diapers different alternatives of closing systems are used today, wherein the closing of the diaper is carried out either by means of an adhesive tape on a film or by means of a hook tape onto a loop layer. Traditional hook/loop variants, generally referred to as hook-and-loop fastener, are the closing systems with higher quality, in the case of which the loop layer consists mainly of textile materials. The customer perceives them as being of a higher quality, because they are also known as closing systems for clothing and shoes. In the case of cost-sensitive products for the temporary or single use, cheaper hook-and-loop alternatives must be used, which can be produced at lower cost structures. In the area of absorbent disposables, in particular diapers, such hook-and-loop fastening devices are described e.g. in WO 96/22065, EP 719 533, EP 721 770 and WO 95/25496.

The use of existing hook-and-loop fasteners on products for temporary or single use is limited due to the costs of the fasteners, relative to other fastening types. The demand for cost-efficient solution alternatives is thus a high priority for this product group, specifically for absorbent disposables, such as diapers.

For this reason, attempts have already been made early on to develop loop systems based on non-woven materials. The non-woven materials produced by means of the initially typical processes, had to be post-treated, so as to shape the fibers to form a loop-forming fiber mat (e.g. subsequent special thermal bonding).

Even though the outer layers of absorbent disposables, in particular of diapers, are preferably produced with a surface, the appearance and the feel of which are as similar as possible to a textile fabric when being touched. For this purpose, a composite of liquid-tight film and a non-woven is mostly foreseen as outer layer as textile-like outer layer. In spite of the successes in this regard, however, the current surfaces are for the most part not sufficient to directly hook the male hook component of a hook-and-loop-fastening device into this surface. The adhesive forces attained hereby are too small.

A formation of the entire outer surface with the volume of the non-woven, which is required for this purpose, is not prudent for cost reasons, because this is only possible via non-wovens comprising a higher thickness or higher grammage of the non-woven, respectively. For example, a non-woven can provide for a sufficient adhesion by means of a corresponding folding. For costs reasons, however, steadily reduced material consumption is called for and the increasingly reduced material thicknesses, approximately 15 to 30 g/m² are currently typical, do not make it possible to offer a surface, which is suitable as loop component, at reasonable costs even with a prestretching by means of ring rolling. Compared to correspondingly more voluminous non-wovens made of the prevalent polyolefin materials, the currently typical polyester fabrics or knitted fabrics as loop component, which are produced separately and which are applied to the back sheet, are more cost-efficient in spite of the considerably higher material price of the polyester non-woven and the additionally necessary fastening step.

As solution, WO 98/11855 proposes a loop component, which is embodied in one piece with the outer layer (back sheet) of a disposable. For this purpose, the back sheet is to consist of each one inner and one outer layer, which are connected to one another, wherein the outer layer of non-woven is imperatively made to be sufficiently voluminous by means of prestretching in the landing zone area/loop area and is not connected to or less connected to the inner layer in the area, which later forms the loop component of the hook-and-loop fastening device. In the case of this method, however, the area of the landing zone must be produced in particular with the help of the prestretching for a sufficient closing force, too.

EP 1 915 918 proposes a method for producing composites, which are suitable as loop component of hook-and-loop fasteners, in the case of which a film and a non-woven are brought together on a heating cylinder, wherein the heating cylinder heats the film to the molten state. Thereby, a composite of film and non-woven is formed, which is allowed to shrink by 1 to 10% in machine direction, so that the non-woven increases in height by the reduction of its dimension in the surface. The composite is subsequently cooled to a temperature of below the melting temperature of the film in a cooled roll nip. Such composites are suitable as back sheet and allow for the anchoring of hooks, particularly hooks adapted in a specific manner, to the non-woven. This method requires for the film to shrink in the heat and does not allow for the non-woven on its own to be attached to an article as loop component.

A spunlaced non-woven is described in US 2009/0068394 A1 as loop component, which imperatively encompasses 3 to 80 openings per m², in which the fibers, which are hooked into one another, are intact on the lateral walls of the openings. The non-woven only allows for a small number of opening and closing cycles, because it already encompasses relatively high fiber disintegration in response to low opening cycles. It is also suitable to be used as back sheet. With 33 g/m², however, the grammages in the examples are still relatively high and US 2009/006839 A1 thus proposes the use of strips of the non-woven material, which are fastened subsequently, as loop component. In addition, the introduction of the openings is time-consuming.

Thus, the object remains to simplify the production of hook-and-loop fasteners or to provide for it in a more cost-efficient manner, respectively, in the case of absorbent disposables.

Surprisingly, it was now found that spunlaced non-woven materials of continuous filaments encompass the necessary loop-like fibrous web, into which the hook component of hook-and-loop fasteners can be hooked, even without a post-treatment or the connection to a further material layer.

The present invention thus solves the above-mentioned problems of the known materials with the use of a spunlaced non-woven material of continuous filaments as loop component of hook-and-loop fasteners. The object is further solved by a loop component for hook-and-loop fasteners, which comprises a spunlaced non-woven material of continuous filaments.

According to the invention, spunlaced continuous filament non-wovens are used. Due to their production process, the spunlaced non-woven materials of continuous filaments provide for a fibrous web, which is embodied in a loop-like manner and which thus provides sufficient possibility to the hooks for being anchored.

Non-woven materials with a grammage of 10 g/m² to 50 g/m², preferably of 15 to 30 g/m², are well suited. In individual cases, the grammage can be up to 150 g/m². The fiber structure, that is, the openness of the non-woven material as well as the intertwining degree of the individual fibers can be influenced and controlled specifically by means of the process parameters of the spunlacing, so as to design the loops, which are generated by means of the water jets, to be larger or smaller, tighter or looser. This takes place by varying the water pressure, the water quantity and/or the number and arrangement of the water jets. It is also possible to create a non-woven material comprising a loop-in-loop structure, similar to a knitted material, by means of water jets. Spunlaced non-woven materials of continuous filaments can be obtained commercially from RKW SE under the name HyJet®, for example.

It is advantageous that spunlaced non-woven materials of continuous filaments can be used as loop component without further treatment according to the invention. In particular, it is not necessary to introduce defined openings and preferably this also does not take place. The irregularly distributed opening structures, which are present in the structure of the non-woven material, need to be differentiated from the openings introduced according to the state of the art and are not considered to be openings.

It is furthermore advantageous that a bond is also not necessary, neither by introducing bonding points, nor by providing bonded areas comprising non-bonded points/surfaces.

Depending on the type of the used hook variants, the degree of freedom of the formed loops, however, can be influenced additionally or can be defined in a specific manner, respectively, in that the fibrous web is bonded at discrete locations by means of thermal solidification and/or ultrasonic welding and/or adhesion. A bonding of the fibers in an area of 1-25%, preferably 2 to 20% of the entire area, is sufficient here. This bonding can take place before or after the spunlacing. A thermal solidification, in particular by means of a thermobonding calander, is preferred. The degree of solidification can be adjusted specifically by means of the parameters thereof. The bonding can thereby take place in a punctiform manner with different geometries, such as circle, ring, rhombus or in a line shape.

It has also been surprisingly found that a non-woven material of continuous filaments which is only slightly pre-consolidated, e.g. by bonding points, can be treated by water jets so that the jets of water specifically release filaments from the bonding. This, too, can provide non-wovens with the loops necessary for the hooks. It is important that the water jets do not tear the filaments when releasing them from the bonding. Preferably, jets are targeted in an in-line process at an already thermally bonded spunbond such that individual filaments are released again from the thermal bonding and so as to provide loops for the hooks. Thereby the degree of loop formation can be optimally adapted to the respective hook regardless of the gravure design. In order to release the filaments from the bonding, this connection may not be too strong, however. One has, for example, in the case of thermal bonding to select a combination of calender pressure and temperature, which allows the water jets to remove single filaments from the bonding points. The fibers must not be torn but only released from the bonding, such that larger loops are formed thereby, into which the hooks can penetrate easier and find optimum grip.

The non-woven material as such can be placed against the provided location, e.g. on the outer skin of the diaper, during the production of diapers or other products, and thus provides the target surface for the hook tapes, which is designated landing zone. The placement is hereby carried out by means of a fastening, preferably adhesion, to e.g. the outer diaper skin, whereby the continuous filaments are fastened to the bottom side of the non-woven on the outer skin. The degree of freedom of the individual loops is limited by means of this adhesion and is adapted to the requirements of the hook material.

An alternative embodiment is to connect the non-woven material according to the invention to a further layer, preferably a polymer film, so as to realize a prefabricated non-woven film composite as back sheet or landing zone material, thereby. Different processes are available for this: direct extrusion (e.g. by means of vacuum or in the roll nip), nozzle coating, adhesive lamination, all of which are useful.

By varying the process parameters, the penetration depth of the loop material into the film surface can be controlled during direct extrusion, so that the available loop size and length can be modified specifically in accordance with the used hook materials. On principle, all methods for applying polymers (or EVA, hotmelt, etc.) are suitable to attain a defined integration of the loop material, wherein the polymer application can take place across the entire surface as well as in defined partial surfaces. The loop size and length can also be controlled by means of an application across a partial surface.

A composite of spunlaced non-woven materials of continuous filaments with a film, which is produced by means of the thermal laminating processes, which is known from WO 2006/024394, is particularly preferred. The production of a cost-efficient landing zone alternative in response to a simultaneous control of the loop formation is possible in a particularly easy and reproducible manner with this. According to the invention, the penetration depth of the non-woven material loops into the film layer can be defined exactly here and the loop geometry can thus be adapted to the different hook geometries in an ideal manner. In contrast to EP 1 915 918, however, a shrinking of the composite is avoided according to the invention; the non-woven material shall essentially not change its surface area. A slight shrinkage of up to 1%, preferably of up to 0.5%, e.g., however, does not interfere.

The penetration depth of the film material or adhesive, respectively, into the non-woven material can be between 1 and 50% of the non-woven material, preferably between 10 and 40%. Good fastening characteristics of the loops are thereby attained, without the non-woven material losing its textile-like, soft surface. The penetration depth should be at least 1%, preferably at least 2% of the thickness of the non-woven material, so that the loops are not detached from the non-woven material too much when the hook component is detached.

All spinnable polymers, such as e.g. polyester, PLA, polyolefins, in particular polypropylene and polyethylene, for example, are suitable as material for the production of the continuous filaments for the non-woven materials. Generally, other polymers, which allow a spinning into fibers, can also be used. In a particularly preferred manner, the continuous filaments and thus the non-woven material consists of polypropylene material and/or polyethylene material or a biodegradable material. The material thereby contains polypropylene and/or polyethylene or a biodegradable material and the typical additives, such as processing aids, e.g., as well as possible production-related constituent.

The filaments should encompass a thickness of between 10 and 70 μm, so as to ensure a textile character on the one hand and so as to guarantee a sufficient filament stability on the other hand.

The required values of the hook shear forces of >10 N/2.54 cm are achieved with the non-woven materials or composites, respectively, according to the invention for typical hooks, e.g. by Binder, Velcro, 3M. Typically, shear strengths of 10 to 100 N/2.54 cm, preferably of 20 to 80 N/2.54 cm, particularly preferred of 30 to 70 N/2.54 cm are reached. In response to the opening, a maximum peel force of 30 N/2.54 cm is not exceeded. Preferably, the peel force is in the range of 1 to 25 N/2.54 cm, preferably of 3 to 15 N/2.54 cm. Also upon repeated opening and closing, the fibers are not pulled out of the non-woven material to such an extent that the hook forces fall below the desired values or that the non-woven material appears to be ruffled.

The invention is to be explained by means of the figures below, however, without being limited to the specifically described embodiments. Unless otherwise stated or unless there are compelling facts that follow from the context, the percentages refer to the weight, in case of doubt to the total weight of the mixture.

The invention also refers to all of the combinations of preferred embodiments, unless they are mutually exclusive. The designations “about” or “approx.” in combination with a number mean that values, which are at least 10% higher or lower, or values, which are 5% higher or lower, and values, which are 1% higher or lower in any event, are included.

FIG. 1 shows a non-woven material according to the invention.

FIG. 2 shows a non-woven material according to the invention comprising discrete bonding points.

FIG. 3 shows a composite of non-woven material and film.

FIG. 4 shows a further composite of non-woven material and film.

FIG. 5 shows a diaper.

A section of a non-woven material according to the invention is illustrated schematically in FIG. 1. The non-woven material 1 neither has bonding points nor openings or other inhomogeneities. The structure attained by means of the spunlacing alone already forms sufficiently voluminous loops, so that the typical hooks attain the necessary adhesion. Such a non-woven material can be laminated onto a diaper or another sanitary product or onto disposable clothing as landing zone. By fastening the filaments to the support, the loop structure is fastened and the detachment of the continuous filaments is limited.

FIG. 2 shows an embodiment wherein the loop structure is fastened specifically by means of discrete bonding of the fibers at the bonding points B, which assume an area of 1-25% of the total area. This bonding can take place thermally, by means of ultrasound or chemically by means of adhesives. The form of the bonding points B can be chosen in a manner, which is known per se; for example circle, rhombus, square, etc., in each case filled or unfilled, or in a line shape are suitable.

FIG. 3 shows an embodiment wherein the non-woven material 1 is laminated with a film 2. For the lamination e.g. the direct extrusion process or also the thermal laminating process described in WO 2006/024394, is suitable. The material of the film 2 thereby penetrates into the non-woven material 1. Penetration depths of 1-50% of the non-woven material thickness thereby turned out to be suitable.

In a fourth embodiment, which is shown in FIG. 4, film 2 and non-woven material 1 are laminated by means of adhesive. In this case, the connection can be made across the entire surface or also only across the partial surface. The adhesive material can be applied in a punctiform or line-shaped manner, for example.

FIG. 5 illustrates the set-up of a diaper. The outer skin of the diaper is formed of a composite of non-woven material and film, the back sheet 4. The loop component must at least be present in the landing zone 5. In that location, a loop component according to the invention of non-woven material 1 or of non-woven material 1 and of film 2 is applied, e.g. by means of adhesion, or the entire back sheet is formed of a composite of non-woven material 1 and film 2. A typical diaper furthermore has an elastic cuff 7 in the waist as well as elastic leg gathers 8. The suction core 9 is arranged between the back sheet 4 and a top sheet and typically encompasses a mixture of absorbent fibers, such as cellulose wadding and a super absorber. Super absorbers are polymers, which can absorb several times their own weight in liquid.

EXAMPLES

Determination of the Shear Force

Means: loops-specimen  50 mm * 150 mm hook tape 25.4 mm * 20 mm   metal plate  50 mm * 150 mm rolling device 2 kg + 5 kg adhesive tape one-sided (25.4 mm) and two-sided (50 mm)

The loop specimen is adhered to the metal plate by means of a double-sided adhesive tape and is rolled down 2 times by means of the rolling device 2 kg without pressure. The hook tape is adhered to the one-sided adhesive tape. This hook tape is fastened to the loop specimen in the center of the narrow side, which is 50 mm wide, and is loaded 4 times by means of the rolling device with 5 kg. The loop specimen is clamped into the pulling device on the bottom and the shear force 180° is determined in N in response to a withdrawal speed of 300 mm/min.

Determination of the Peel Force

Means: loops-specimen   50 mm * 150 mm hook tape 25.4 mm * 20 mm weight  500 g for hanging adhesive tape one-sided 25.4 mm wide 100 mm long clamp   2 pieces, 50 mm wide

The hook tape is fastened to the center of the one-sided adhesive tape. The hook tape is fastened to the center of the non-woven specimen and is pressed together for 3 seconds using 2 fingers. The hook specimen is then hung up vertically and the hook tape is loaded for 5 seconds with 500 g (shear direction). The loop specimen is clamped vertically on the bottom in the pulling device and the hook tape end, which points downward, is clamped into the pulling device on the top and the peel force is determined in N in response to a withdrawal speed of 300 mm/min.

All of the shear and peel forces are determined according to the invention in accordance with the above methods. The forces are specified in N/2.54 cm (N/inch). A conversion into N/1 cm is not possible; for other dimensions, determinations must be made on specimens comprising these dimensions.

Example 1

A purely spunlaced non-woven material of continuous filaments in a weight class of 35 g/m² was used as loop component of a hook/loop closing system for an adult incontinence product. The non-woven, RKW HyJet® 35 g/m² was thereby used in the form of a belt across the entire width of the incontinence product and the closure took place by means of a hook by Binder, Mikroplast 65445-C. The shear forces determined for the specimens are 65 N, the peel force values are 45 N.

Example 2

A 25 g/m² spunlaced non-woven of continuous filaments, RKW HyJet® 25 g/m², comprising a polypropylene film with a weight of 20 g/m² was laminated as landing zone material for a baby diaper, so that the total composite encompassed a weight of 45 g/m². Sections of this laminate with a size of 15×4 cm were applied to the stomach area (landing zone area) of the diaper. The hook tapes, for example the hook variant by Binder, Mikroplast 25445, can then be anchored in this area of the diaper for the purpose of closing the diaper. The shear forces determined for the specimens are 45 N and the peel values are 7 N.

LIST OF REFERENCE NUMBERS

-   1 non-woven material -   2 film -   3 adhesive -   4 back sheet -   5 landing zone -   6 hook tape -   7 cuff -   8 leg gathers -   9 suction core -   B bonding point 

1-15. (canceled)
 16. Use of a spunlaced non-woven material of continuous filaments as female component (loop component) of a hook-and-loop fastening system, wherein no openings are introduced into the non-woven material and the non-woven material does not encompass any bonding prior to the spunlacing.
 17. Use according to claim 16, wherein the continuous filaments of the spunlaced non-woven material are bonded in defined areas, wherein the bonding is 1-25%, preferably 2 to 20% of the total surface.
 18. Use according to claim 16, wherein the non-woven material is connected to at least one further layer, preferably a film, preferably by means of extrusion coating, adhesive lamination, ultrasound welding or by means of thermal lamination.
 19. Use according to claim 18, wherein the loops of the non-woven material penetrate into the material of the further layer or an adhesive, with which the non-woven material and the further layer are connected, to 1 to 50% of the thickness of the non-woven material.
 20. Use according to claim 16, wherein the non-woven material is applied to an absorbent article, in particular a diaper or pad, as loop component for fastening the latter.
 21. Use according to claim 18, wherein the non-woven material, which is connected to the further layer forms the back sheet of a sanitary product, in particular of a diaper. 